Oh, I've had a few instances where my game file got messed up because of some accident. And yep, it's pretty frustrating when it happens, so I understand how you feel.

First one that comes to mind would be my favorite save file from FF VII. It was one where I was working on leveling up a bunch of materia to master level, and also the file that had my gold chocobo in it, the only one I ever got too. One day, I turn on the PSX to continue working on my game, and discover that one of my brothers accidentally saved his game over my game! I was so disappointed that all my hard work just disappeared like that...

I also tripped over my PS2 controller cord, and knocked off the console into the floor while I was playing FF XII. The disk popped out of it, and got scratched up. I thought it was okay at first, but about the time I got to Archades, I was having a lot of issues with the game freezing up... I took the disk to get repaired, but it still won't play the entire ending... I had to watch that on Youtube.

Final story, and then I'm done. I was playing KH2 for the first time, and was just getting around to exploring the mansion in Twilight Town while playing as Roxas, and all of a sudden the power just goes out! For some reason, I had not saved at all up to that point, so I had to play the whole opening again! I didn't want to redo all the tutorials, but I had no choice but to do just that... Now, I make sure to save frequently, even if I plan on playing for a long time.